Re: Hard shifts in 2004 K2500 Suburban

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Posted by OnBelay ( on 06:36:47 05/22/08

In Reply to: Hard shifts in 2004 K2500 Suburban posted by CharlieT

Sorry for the ugly cut and paste, but a visit to a dealer is in order for TSB No. 08-07-30-001

Date: January 16, 2008

4L80E, MT1 and 4L85E, MN8 Simplified Valve Body Reconditioning Instructions DTC P0741, P0742, P0751, P0752, P0756, P0757, P0894 Harsh or Delayed Shifts Slips No Drive No Reverse

This bulletin is designed to provide easy to follow valve body reconditioning instructions and new illustrations to simplify reassembly of the valve body and list other service information documents that are related to the 4L80X transmission family.

Related Service Document

PIP3427A - SES light on DTC P0757 harsh shifts delayed 2-3 shift no third gear or slip in third or reverse or a 2-3 shift flare. Debris stuck in the # 11 check ball or a sticking pintle in the 2-3 shift solenoid.

Inspection Procedure

Using the exploded view (Illus. A) inspect each bore for freedom of valve(s) movement and evidence of debris. Pay particular attention to those valves related to the customers concern. IF VALVE BODY CLEANING IS NOT REQUIRED, DO NOT DISASSEMBLE BORES UNLESS IT IS NECESSARY TO VERIFY MOVEMENT OF VALVES.

Verify movement of the valves in their normal installed position. Valves may become restricted during removal or installation. This is normal due to small tolerances between the valves and bores.

If a valve is restricted and cannot be corrected by cleaning the valve and bore then replace the valve body. Describe the restricted valve on the repair order.


If a valve is restricted by a metal burr from machining that bore remove the valve and burr then inspect movement in the valve's normal position. If no other debris or restrictions are found then reassemble the valve body and install in the transmission.

If the valve body has been contaminated with debris from another transmission component failure then disassemble all bores for complete cleaning of all valve body components. Keeping individual bore parts separated will make reassembly easier. Use the illustrations for positive identification and location of individual parts.

Using GM Brake Clean or equivalent in a safe and clean environment (clean aluminum pan) clean the valve body and dry it with compressed air. Use appropriate eye protection.

Clean individual valve body components with GM Brake Clean or equivalent. Coat each valve with clean ATF and reassemble in each bore. Check each valve for free movement during assembly of each bore.

Position the valve body as shown in the illustrations for positive identification and location of individual parts.

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